diff --git a/upup/pkg/fi/BUILD.bazel b/upup/pkg/fi/BUILD.bazel
index 251c5fd848..cf87f577b8 100644
--- a/upup/pkg/fi/BUILD.bazel
+++ b/upup/pkg/fi/BUILD.bazel
@@ -68,6 +68,7 @@ go_test(
     size = "small",
     srcs = [
         "dryruntarget_test.go",
+        "files_test.go",
         "vfs_castore_test.go",
     ],
     embed = [":go_default_library"],
diff --git a/upup/pkg/fi/files_test.go b/upup/pkg/fi/files_test.go
new file mode 100644
index 0000000000..10f134a641
--- /dev/null
+++ b/upup/pkg/fi/files_test.go
@@ -0,0 +1,86 @@
+/*
+Copyright 2020 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package fi
+
+import (
+	"bytes"
+	"io/ioutil"
+	"os"
+	"path"
+	"testing"
+)
+
+func TestWriteFile(t *testing.T) {
+	var TempDir, _ = ioutil.TempDir("", "fitest")
+	defer os.Remove(TempDir)
+	tests := []struct {
+		path     string
+		data     []byte
+		fileMode os.FileMode
+		dirMode  os.FileMode
+	}{
+		{
+			path:     path.Join(TempDir, "SubDir", "test1.tmp"),
+			data:     []byte("test data\nline 1\r\nline 2"),
+			fileMode: 0644,
+			dirMode:  0755,
+		},
+	}
+	for _, test := range tests {
+		err := WriteFile(test.path, NewBytesResource(test.data), test.fileMode, test.dirMode)
+		if err != nil {
+			t.Errorf("Error writing file {%s}, error: {%v}", test.path, err)
+			continue
+		}
+
+		// Check file content
+		data, err := ioutil.ReadFile(test.path)
+		if err != nil {
+			t.Errorf("Error reading file {%s}, error: {%v}", test.path, err)
+			continue
+		}
+		if !bytes.Equal(data, test.data) {
+			t.Errorf("Expected file content {%v}, got {%v}", test.data, data)
+			continue
+		}
+
+		// Check file mode
+		stat, err := os.Lstat(test.path)
+		if err != nil {
+			t.Errorf("Error getting file mode of {%s}, error: {%v}", test.path, err)
+			continue
+		}
+		fileMode := stat.Mode() & os.ModePerm
+		if fileMode != test.fileMode {
+			t.Errorf("Expected file mode {%v}, got {%v}", test.fileMode, fileMode)
+			continue
+		}
+
+		// Check dir mode
+		dirPath := path.Dir(test.path)
+		stat, err = os.Lstat(dirPath)
+		if err != nil {
+			t.Errorf("Error getting dir mode of {%s}, error: {%v}", dirPath, err)
+			continue
+		}
+		dirMode := stat.Mode() & os.ModePerm
+		if dirMode != test.dirMode {
+			t.Errorf("Expected dir mode {%v}, got {%v}", test.dirMode, dirMode)
+			continue
+		}
+	}
+}